[GAMEPLAY] Kindred not stacking Baron mark

Hello, I play a lot of Kindred and I noticed that sometimes he won't stack a mark. I made a mental note of when this happens and last time it did, today, was for the Baron's mark. The baron was marked and when he was defeated with smite, it played the sound of a mark collected. However, no mark was collected. I have no idea why it did not stack the mark, but I was airborne when I smited it (knocked up by Baron), so that might play a role in it.

Cheers!